Imaging and optical sensing devices are widely used in both commercial and military applications. In traditional configurations of focused optical imaging or sensing systems, a sensor array is located in the image plane and oriented perpendicular to the optical axis. This configuration is necessary to keep the image in focus across the entire active area of the imaging detector; however this configuration makes the system retro-reflective. As a result, any light not absorbed by the sensor (e.g., a camera or focal plane array sensor) is reflected and imaged directly back to the source along the same optical path as the incident light (i.e., retro-reflected).
Optical augmentation (OA) systems use this property of retro-reflection to detect hidden optical systems. For example, an OA interrogator uses an active light source to sweep through an environment, illuminating any target optical devices. Traditional optical systems produce a “cat's eye” effect in which any unabsorbed light from the illuminating beam is retro-reflected back to the OA interrogator. The retro-reflection reveals the location of the illuminated target optical system, as well as type of sensor used in the system. The sensor type may be linked to the type of hardware it supports, along with its the associated capabilities and vulnerabilities.